@wetfeetons-checkbox syntax was introduced in version 2.4.0 version of Onsen UI. You are most likely using an older version and probably getting errors in your console. Can you check if that’s the case?

@wetfeet that 2.2.1 is just the Monaca CLI version you’re using. For the Onsen UI one on that project you can check www/lib/onsenui/package.json. In any case I just tried and even the latest CLI version only fetches 2.3.2 so the templates are not updated yet. If you really want to use Onsen UI 2.4.0 with Monaca you can either wait for the update or change your index.html file’s head to fetch from CDN. Or you can also download the 2.4.0 version and add it to the lib instead of the current one.